1. Field of the Invention
The present invention relates to a sewing apparatus for manufacturing a tubular piece made of knit fabric or other elastic material, such as a cuff and anklet sewn to, for example, sweat wear, jackets and sweat pants.
2. Description of the Prior Art
Hitherto, manufacturing such a tubular piece, was generally based on manual work, requiring cutting a long tape into a specific size, folding the cut tape in two in the widthwise direction to join the ends, leading the joined edges into the sewing part of the sewing machine while keeping the folded shape by the hand of the operator, and sewing. It took, accordingly, too much time and labor, resulting in poor productivity, thereby raising the cost of manufacture.
In light of the problems associated with the conventional manual work approach, a tubular piece manufacturing apparatus has been proposed which is capable of automating the procedure of the tubular piece manufacture. Such an apparatus is disclosed in Japanese patent application Hei. 1-19269.
The apparatus disclosed in this Japanese patent application comprises a leading-out device having an air cylinder with a long stroke for gripping the end portion of a long tape guided on a guide surface, and drawing out the long tape by a specified length; a pair of gripping pieces for holding the end portions of the long tape to shift it from the leading-out device; an inverting device for inverting the tape gripped part by the gripping pieces and overlaying on the long tape on the guide surface after the long tape is sent out to a specified length by a sending-out device; a cutting device for cutting the long tape so as to form an edge portion opposite to the edge portion of the tape folded back by the inverting device; and a conveying device for conveying the tape folded part formed by the cutting device so that the opposing edge portion may be led into the sewing part of the sewing machine sequentially.
The tubular piece manufacturing apparatus so constructed is capable of automating the work that took much time and labor in the conventional manual work approach, enhancing productivity and lowering the manufacturing cost. This apparatus proved very useful, but the following points still require improvement.
(1) The leading-out device has an air cylinder with a long stroke, and has a gripping device attached to the front end of the rod of the air cylinder, and the air cylinder is disposed to extend in the lengthwise direction of the guide surface.
Accordingly, the apparatus itself is long in the longitudinal direction, and is large in size, and requires a wide area for installation.
In addition, since the gripping device is attached to the front end of the rod, and the rod projects horizontally to grip the long tape, the gripping action may be unstable in the course of long use due to deflection at the front part of the rod and vibration or other effects. There is room for improvement in the durability aspect of the apparatus.
(2) By the sending-out device, the tape is sent out upon completion of the retraction action of the air cylinder after the inverting device returns to its initial state (the gripping pieces are open vertically in the forward position of the guide surface), only after the tape end portion held by the leading-out device is shifted to the gripping pieces.
Therefore, the number of tubular pieces manufactured per unit of time is limited by the time required for retraction of the air cylinder and the time required for the shifting action to the gripping pieces; and, in order to improve manufacturing efficiency, it is required to shorten these action times as much as possible.
(3) Since the conveying device passes before the sewing machine, it is necessary to install a guide shaft or other guide member at the front side of the sewing machine for reciprocal motion of this conveying device. This guide member, however, becomes an obstacle when serving the front part of the sewing machine.